The present invention relates to a method for limiting the rotational speed of internal combustion engines with spark ignition.
German Patent Document DE 33 19 025 C2 describes a method and a device for limiting the rotational speed of internal combustion engines having spark ignition, whereby on reaching a first definable rotational speed value, the fuel mixture is made leaner and the ignition sequence is worsened and at a second rotational speed value, which is greater than the first rotational speed value, a switch is made to a much leaner fuel mixture.
In comparison with the known method, the method of the present invention has the advantage that the combination of a soft rotational speed limitation and a hard rotational speed limitation complies with demands for comfort while also complying with demands for an extremely sporty driving performance in vehicles having high-performance engines. In internal combustion engines having high-performance engines, reducing torque only through injection fade-out and delaying injection results in excessively high rotational speed amplitudes in the area of the desired maximum rotational speed, which is perceived as unpleasant by the driver. In contrast, limiting the rotational speed by regulating the throttle valve on the vehicle cannot be perceived directly by the driver with a very sporty driving style and for power measurements.
In accordance with the method of the present invention, the function of the hard rotational speed limitation is implemented in such a way that the duration of the cylinder fade-out and the interval of the fade-outs and/or the non-fade-out of the engine are applied in any way desired via a control unit. The duration of turning the injection on and off with or without ignition intervention can be adjusted in any way and at the same time is regulated via intervention involving the electric throttle valve.
Another advantage is obtained with the inventive control method due to the fact that the switching between a hard and a soft rotational speed limitation can be adjusted according to the desired driving performance. Thus, it is conceivable for the control to first trigger a hard rotational speed limitation and later to switch for several seconds to a soft rotational speed limitation or vice-versa. The background for such switching from hard and soft rotational speed limitation may be provided by the requirements of the engine and the catalytic converter. The change from a soft to a hard rotational speed limitation may be desirable when the driver is to receive feedback that he should shift to the next higher gear.
Another advantageous embodiment is possible with the inventive rotational speed limitation due to the fact that different maximum rotational speeds may be regulated for any period of time and for any gears. The driving performance of the internal combustion engine can thus be adapted even better to various requirements. All the variables to be controlled can, for example, be stored in a control unit and can be determined in the application.
The inventive triggering is explained in greater detail below with reference to the figures.